""Do you think they helped much for the bottom end response and torque the website mentions?""

I have used a handfull of carbs on this 340 (Edy 600, Edy 750, 650 Speed Demon DP, the same Demon modified with Proform main body and Proform metering plates, and a Promax street/strip 650 vacuum secondary). The annular DP gives me the best overall performance of any of these previous carbs. But,,,,, it came stock very rich and it was a dog when I first got it three years ago. I've tuned it and it quickly became the best carb that I have used so far. Then recently I started tuning it with an O2 sensor and the carb is more reactive than before. My fuel curve is now correct and I think that it is an excellent street carb for my setup. If you order thru QF, then you can have a choice of the anodize color on the outside of the carb (metering blocks and base plate). I chose to have them do mine in black.